This invention relates generally to a device to indicate the presence of potentially dangerous voltages on electrical connections in contact with a tool or other instrument and also to indicate the presence of voltage on a conductor or electrical circuit.
Voltage indicating meters have long been available for testing circuits for the presence of potentially dangerous voltages. More recently, non-contact AC voltage detectors such as the Greenlee Model 38888 have been available. Such devices are only useful if the operator is willing to take the extra time required to test the circuit before working on it. A further problem with these prior art non-contact indicators is that they indicate the presence of an electrical field without contacting a conductor. Thus, there is no way to distinguish which of several adjacent conductors is producing the sensed electrical field. Other voltage indicating devices, such as that described in U.S. Pat. No. 4,724,382 are relatively complex involving high amplification and a constant voltage source to differentiate between full alternating voltage in the main and ripple voltages.
It is therefore a principal object of the present invention to provide a device internal to an electrical tool to alert the user to the presence of potentially dangerous voltages.
It is a further object of the present invention to provide a device for indicating the presence of potentially dangerous voltages to the user without requiring any electrical contact with the user, thereby eliminating the need for protective resistors, foil, and electrodes to insure the user's safety.
It is a further object of the present invention to provide a totally self-contained and waterproof device for indicating the presence of potentially dangerous voltages to the user, thereby eliminating external switches, lights, electrodes, foil, and contacts.
It is yet another object of the present invention to provide a device for indicating the presence of potentially dangerous voltages to the user, the device drawing sufficiently low power from its power source to allow continuous operation for several years without the need to change batteries or disconnect the power source when not in use, thereby insuring against use of the device while inoperative.
These objects are accomplished in accordance with the illustrated preferred embodiment of the invention by providing means for detecting the presence of an AC voltage on a blade or other operative portion of the tool, means for filtering and processing the detected AC voltage, and means for indicating the detected AC voltage to the user.